Correlation of supercritical CO ₂-ionic liquid vapor-liquid equilibria with the ε ^*-modified Sanchez-Lacombe equation of state

The ε*-modified Sanchez-Lacombe equation of state (ε*-modified SL EOS) contains a temperature-dependent interaction energy that allows it to provide better pure component ionic liquid pressure-volume-temperature representation than the original SL EOS. In this work, we applied the Îμ-modified SL EOS to correlate available high pressure CO ₂-ionic liquid vapor-liquid equilibrium (VLE) data, which are important for developing viscosity correlations. Usual SL EOS mixing rules were applied with one interaction parameter, k _ij, which was fitted to the data. For the case of k _ij equal to zero, the Îμ-modified SL EOS could greatly improve the average relative deviation (ARD) of the VLE (ARD 14.6%) over that of the original SL EOS (ARD 44.0%). For the case of k _ij being fitted for both EOS, representation of the VLE of both equations was similar (ARD≤9%). The ε*-modified SL EOS is able to describe the vapor-liquid equilibria data over a wide range of pressures (0.1<<100MPa) and gives semi-quantitative (ARD<15%) representation of CO ₂ solubilities in many ionic liquids from knowledge of only the pure component properties.